Ma'mar bin Rashid معمر بن راشد · Commercial Transactions (Kitab Al-Buyu)

The Prophet (ﷺ) said: After the grave sins which Allah has prohibited the greatest sin is that a man dies while he has debt due from him and does not leave anything to pay it off, and meets Him with it.

The Prophet (ﷺ) forbade two types of business transactions and two ways of dressing. The two types of business transactions are mulamasah and munabadhah. As regards the two ways of dressing, they are the wrapping of the samma', and that when a man wraps himself up in a single garment while sitting in such a way that he does not cover his private parts or there is no garment on his private parts.